Pump Glossary

Common Terms Used in the Pump Industry

Acidizing

Air Entrainment

When air gets trapped in the pump’s suction line. Usually caused by some type of leak in the suction line. Air entrainment significantly reduces the pump’s performance.

Anti-Vortex Plate

Prevents the formation of a vortex, which causes air entrainment. The vortex is prevented by forcing it around a plate and into the suction pipe. This interrupts the swirling motion, and the vortex dissipates.

Atmospheric Pressure

Refers to the pressure in the local environment of the pump. Atmospheric pressure varies with elevation: 14.7 psi at sea level, decreases with rising elevation.

Baseplate

Steel base that anchors the pump and motor to a concrete base.

Basket Strainer

Type of filter; a cylinder with holes in it designed to prevent solids from entering the system with the flow of water. The smaller the holes, the better the filtration.

Bypass Line

A line connecting the pump’s discharge line to a low pressure area, usually the pump’s suction tank. A bypass line moderates the flow in the system.

Casing

The body of the pump, which encloses the impeller. Also called the chamber, housing, or volute.

Capacity

How much water a pump is capable of delivering at a specific head; expressed in terms of GPM or cubic meters per hour.

Cavitation

Occurs when bubbles inside the impeller collapse after being rapidly compressed by the pressure created by the impeller vane. Cavitation causes damaging pitting and erosion to the impeller. Pump design, temperature and pressure of the liquid being pumped, and pump design determine whether or not cavitation will occur.

Centrifugal

Moving or directed outward from the center of a rotating object; the force caused by the rotation. Example: when riding a merry-go-round at the playground, you can feel centrifugal force pulling you away from the center. The faster the merry-go-round spins, the stronger the force.

Chlorination

Treating wells with chlorine compounds to fight the growth of algae and bacteria.

Check Valve

Prevents water from flowing in reverse, down the discharge pipe and back into the pump. If the water flows back into the pump, it could rotate the impeller in the reverse direction, causing damage.

Closed Impeller

The vanes on a closed impeller are sandwiched between two disks, called a shroud. This keeps the water in constant contact with the vanes. More efficient than an open impeller, but also more prone to clogs.

Cut In

A pre-set pressure level inside a pressure tank. Once the pressure drops to this level, the pump is signaled to switch on, refilling the tank and raising the pressure level.

Cut Out

A pre-set pressure level inside a pressure tank. Once the pressure rises to this level, the pump is signaled to switch off.

Cutwater

- the narrow gap between the impeller and the pump casing at the discharge point. Every time a vane of the impeller passes this point, it creates a pulse. To reduce the force of the pulsations, more vanes are added to the impeller. This decreases the volume of water being pushed by the individual vanes, which reduces the force of the pulsation created at the cutwater point.

Dead Head

Occurs when the pump is running but the discharge pipe is closed. May be caused by a clog in the pipe or a mistakenly closed valve. The pump will go to maximum head and the water will re-circulate, causing the pump to overheat and potentially damaging the pump.

Diaphragm

A flexible wall inside a pressure tank or diaphragm valve which separates the water from the compressed air.

Diffuser

A set of fixed vanes that surround the impeller, creating a less turbulent area were the water, after being compressed by the impeller, can expand more slowly, decreasing in velocity as it expands. This increases the pump’s efficiency.

Dishcharge Line

The pipe water is pumped into from the pump; connects pump to the rest of the water system.

Drawdown

The drop in water level inside a well that occurs when water is being pumped out.

Drive Shaft

Metal rod that connects the impeller to the body of the pump; rotates the impeller.

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Friction Loss

Pressure loss that is a result of the friction created by water moving through the system.

Gland

Attaches to the backplate of the pump; connects to the stuffing box and forms a seal around the drive shaft.

Head

:

head, dynamic

- specific energy in a flow system.

head, discharge

- pressure head at the outlet of the pump.

head, elevation

- head as a result of elevation above a defined datum.

head, friction

- energy head loss caused by the friction of water flowing through a pipe.

head loss

- energy loss in fluid flow.

head loss, converging and diverging pipes

- energy loss associated with water flowing through converging or diverging pipe sections.

head loss, entrance

- energy loss associated with water flowing through the entrance of a pipe.

head loss, bends

- energy loss associated with water flowing through a bend in a pipe.

head, pressure

- pressure energy in a liquid system expresses as the equivalent height of a water column above a given datum.

head, static

- energy associated with a static liquid system composed of elevation and pressure components.

head, static discharge

- static energy components at the discharge of a pump including elevation and pressure.

head, static suction

- vertical distance from the pump centerline to the surface of the liquid when the liquid supply is above the pump.

head, total (Dynamic)

:

Head required to pump water from its source to the point of discharge. Equal to the static lift plus friction head losses in pipes and fittings plus velocity head.

Sum of static, pressure, friction and velocity head that a pump works against while pumping at a specific flow rate. (Reference Manual)

head, total suction

- head required to lift water from the water source to the centerline of the pump plus velocity head, entrance losses and friction losses in suction pipeline.

head, vapor pressure

- pressure head at which the liquid (water) will vaporize or boil at a given temperature.

head, velocity

:

Head or energy caused by the velocity of a moving fluid.

Amount of pressure required to generate a specific velocity. This is the amount of energy or pressure that is used to make the water move at a given velocity.

Horsepower

:

water horsepower

- energy added to water by a pump.

input horsepower

- energy added to a motor or engine

brake horsepower

- power required to drive a pump.

Impeller

A rotating, vaned disk found inside a pump; the impeller spins, creating centrifugal force, which moves the water through the pump.

Inducer

A small impeller that connects to the main pump impeller, and gives the water enough head to meet the NPSH requirement of the main impeller. Prevents cavitation on the main impeller.

Intake Pipe

The pipe that sucks water from the source into the pump housing.

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Lost Prime

Occurs when air enters the pump system, which causes the pump to lose suction and water to drain back out of the system. Until the pump is primed, it can’t pull water, and if it continues to run without water, it will overheat, eventually damaging the pump seal, motor, pipe manifold, etc.

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Net positive suction head

Head that causes liquid to flow through the suction piping and enter the eye of the pump impeller.

NPSHA

Stands for Net Positive Suction Head Available, refers to the available head at the pump suction flange. You have to be sure that the atmospheric pressure will be greater than the suction losses, or vapor will form, causing cavitation.

Open Impeller

An impeller without a front or back disk; the vanes are completely open, resembling a propeller.

Performance curve

Graph showing the capability of a product with varying inputs (i.e. the dynamic head of a pump as it varies with discharge).

Pressure Tank

Pressurized water tank used to stabilize system pressure and prevent the pump from repeatedly cycling on and off.

Priming

Putting water into the pump casing before start up- most pumps require liquid to be present in order to create suction. For example, if you tried to start a centrifugal pump without any water in the casing, the impeller would rotate through air, which would not create the suction necessary to pull water into the pump. Therefore, priming is required to create the initial suction at start-up. Long-term running of a pump without priming first causes unnecessary stress on the motor, overheating, and damage.

Pump

Pump Column

Pipe through which water from a well pump is conveyed to the ground surface (pump discharge head).

Pump Efficiency

Ratio of the water power produced by the pump to the power delivered to the pump by the power unit.

Pump Start Circuit

Feature on automatic controllers which supplies 24 VAC, which can be used to activate a pump through an external pump start relay.

Pump Start Relay

Receives electrical signal from the sprinkler timer directing the pump to open or close. A pump start relay must be used when connecting an irrigation system with a pump; most irrigation timers are 24V, and cannot be connected directly to pumps, which are 110V-220V.

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Self-Cleaning Strainer

A self-cleaning strainer is a filter, similar to a basket strainer, with the added feature of an internal cleaning mechanism, which regularly cleans debris from the filter.

Semi-Open Impeller

The vanes of an open impeller are not sandwiched between two discs; they are backed on one side by a disk, and the other side is open. Open impellers are less efficient, but are also less prone to clogging.

Shaft Sleeve

Casing that protects the drive shaft from corrosion and wear at the seals.

Shear Sensitive

Refers to liquids whose consistency changes as they are stirred. For example, no matter how much you stir water, it will retain is viscosity. Things like paint, latex solutions, polymers, and Ketchup become less viscous (runnier) as they are stirred.

Static Discharge Head

The vertical distance from the pump center line to the surface of the liquid in a discharge tank
or

to the point of free discharge.

Static Head

Energy associated with a static liquid system composed of elevation and pressure components.

Static Water Pressure

Pressure in a closed system, without any water movement. Water pressure when the water is at rest.

Static Suction Head

Vertical distance from the pump centerline to the surface of the liquid when the liquid supply is above the pump.

Static Suction Lift

Vertical distance between the surface of the water source and the pump centerline when the water source is below the pump.

Stator

A stationary shaft in which the rotor spins; the stator fits closely around the rotor.

Swing Check Valve

A valve with a hinged disk inside, which remains closed until water begins flowing into the check valve, at which point the water pressure is enough to swing it open. Prevents water from running back into the system, or, in a pump application, keeps the pump primed when the pump is not running.

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Valve

Device to control flow. Valves commonly used in pump systems include:

ball Valve

- one-way valve that is opened and closed as a result of pressure on an internal ball.

butterfly Valve

- valve in a pipeline to start or stop flow by rotating a disk 90 degrees. The disk is about the same diameter as the pipeline.

check Valve

- valve used in a pipeline which allows flow in only one direction.

chemigation Valve

- valve designed to be used specifically with the injection of chemicals in an irrigation system.

foot valve

- check valve used on the bottom of the suction pipe to retain the water in the pump when it is not in operation.

gate Valve

- valve in a pipeline used to start or stop water flow. May be operated by hand with or without mechanical assistance or by solenoid-controlled mechanical assistance. Gate valves consist of seated slides or gates operated perpendicular to the flow of water.

Velocity

Is the speed at which water moves through the pipe system.

Venturi Effect

The suction effect created by a length of pipe composed of consecutively larger diameter segments. For example, imagine a pipe with five segments running from a water source to a water tank. The first segment is 1” diameter pipe. The second segment is 2” diameter pipe, the third 3”, and so on. The pressure in each larger segment is lower than the pressure in the previous segment. This creates a suction effect, which pulls water up the pipe and into the water tank.

Viscosity

How runny a substance is- if a liquid is “more viscous”, it is less runny.

Volute

The spiral casing around the impeller of a volute pump.

Water Hammer

Shock wave created when the flow of water in a piping system suddenly stops (or changes speed). Usually the result of a fast-closing (or opening) valve.

Water Pressure

In irrigation, pressure describes the amount of energy available to move water through a pipe, sprinkler or emitter.

Water table

Upper surface of a saturated zone below the soil surface where the water is at atmospheric pressure.

Winterization

Process of removing water from the irrigation system before the onset of freezing temperatures.

Working pressure

Pressure of the irrigation system during operating. Synonymous with dynamic pressure.

Wye-Strainer

-
type of filter with distinctive “Y” shape, designed to mechanically remove solids from flowing liquids by means of an internal straining element.

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Y-Strainer

type of filter with distinctive “Y” shape, designed to mechanically remove solids from flowing liquids by means of an internal straining element.